Field of the Invention
This invention relates generally to an electronic navigation calculator, and more particularly to an electronic navigation calculator for making navigation calculations for a moving vehicle such as an airplane which moves with direction and velocity when the airplane is in flight. The invention considers the effects of wind.
Description of the Prior Art
In general, the course made good, the speed and position of a moving vehicle in a moving medium are calculated based upon the speed and heading of the moving vehicle and the direction and velocity of the medium through which the vehicle travels. For example, the ground speed and course of an airplane, which makes a flight in moving air (wind), can be calculated based upon a composite vector of the wind vector and the airplane's airspeed and heading.
A navigation calculation for an airplane flight plan will be now described with reference to FIG. 1 as an example. In FIG. 1, reference letters WD and WS indicate direction and speed of the wind, respectively, TAS the true air speed of an airplane which must fly in the wind, TC the true course of the airplane on an air map or sectional chart, WCA the wind correction angle for the airplane flying on the true course TC, TH the airplane's true heading and GS the ground speed of the airplane, which are calculated by the following equations solving a wind triangle.
______________________________________ ##STR1## .alpha. = TH - TC(=WCA) .beta. = WD - TH .gamma. = .pi. + TC - WD WS sin .alpha. = TAS sin .gamma. GS.sup.2 = TAS.sup.2 + WS.sup.2 - 2TAS .multidot. WS cos .beta. ##STR2## ##STR3## GS = {TAS.sup.2 + WS.sup.2 + 2 TAS .multidot. WS cos (WD ______________________________________ - TH)}.sup.1/2
the above equations are fundamental equations for aircraft navigation. However, in a practical aircraft navigation calculation, complicated calculations such as, for example, conversion of an instrument air speed (IAS) to the true air speed (TAS) correction for magnetic variation, correction for compass deviation correction for speed error, calculation of estimated time enroute, calculation of fuel consumption, fuel on board and time and so on must be carried out.
In order to carry out the above complicated calculations, in the art a dead reckoning slide rule has been known. However, such prior art dead reckoning slide rule requires a great deal of skill for use because it is complicated. Further, such slide rule cannot be operated with one hand, so the a pilot can not perform a navigation calculation with the prior art slide rule while he pilots the airplane and hence the prior art slide rule is limited in use.
In order to ensure a safe flight of an airplane, it is required to prepare an accurate flight plan and to correct the same in accordance with changes during flight. However, in fact if a navigation calculation is complicated and a calculator therefor is difficult to operate such as the prior art slide rule, a navigator or pilot is apt to carry out the navigation calculation incorrectly, which can result in danger.
In addition, the prior art slide rule can not accurately make navigation calculations.